Assembly method for rotary engine

ABSTRACT

The assembly of the rotor and the spring-biased seals carried by the rotor into the housing of a rotary engine is facilitated by applying an adherent, waxy film to the seals and inserting them in the rotor grooves. This film composition adheres to the side of the groove and temporarily holds the spring-biased seals in a recessed position during an assembly operation. However, the properties of the composition are such that the seals self-return after a short time to their normal operating positions for engine starting. Upon brief engine operation the wax composition evaporates and is consumed without residue.

[ Dec. 9, 1975 ASSEMBLY METHOD FOR ROTARY ENGINE [75] Inventor: HaroldW. Ferchland, Troy, Mich.

[73] Assignee: General Motors Corporation,

Detroit, Mich.

[22] Filed: Nov. 7, 1973 [21] Appl. No.: 413,546

[44] Published under the Trial Voluntary Protest Program on January 28,.1975 as document no.

[52] US. Cl 29/156.4 R; 29/423; 29/446; 277/95; 29/469 [51] Int. Cl.B23P 15/00 [58] Field of Search 29/156.4 R, 423, 434, 446, 29/469;418/178, l20-122, 113; 277/95, 81 P [56] References Cited UNITED STATESPATENTS 3,353,830 11/1967 Bell ..277/9.5

3,356,375 12/1967 Harris 277/95 3,492,710 2/1970 Pitner 29/434 3,745,6307/1973 Bensinger 29/l56.4 R

Primary ExaminerRichard J. Herbst Assistant ExaminerDan C. CraneAttorney, Agent, or FirmGeorge A. Grove [57] ABSTRACT The assembly ofthe rotor and the spring-biased seals carried by the rotor into thehousing of a rotary engine is facilitated by applying an adherent, waxyfilm to the seals and inserting them in the rotor grooves. This filmcomposition adheres to the side of the groove and temporarily holds thespring-biased seals in a recessed position during an assembly operation.However, the properties of the composition are such that the sealsself-return after a short time to their normal operating positions forengine starting. Upon brief engine operation the wax compositionevaporates and is consumed without residue.

3 Claims, 3 Drawing Figures US. Patent Dec. 9 1975 3,924,314

ASSEMBLY METHOD FOR ROTARY ENGINE This invention relates to the assemblyof components of a rotary internal combustion engine, particularly ofthe Wankel type engine. More particularly, it relates to a method ofretaining the many spring-biased seals, some in a recessed position, inthe rotor grooves when the rotor is being positioned in the housing ofthe rotary engine.

Rotary engines of the Wankel type are now well known. In the operationof such devices a generally triangular-shaped rotor or piston rotatesinside an epitrochoid-shaped housing. Seals carried by the rotor engagesurfaces of the housing so that a number (frequently three) of separatespaces or cavities of varying volume are established. The various sealscarried by the rotor are usually spring-biased so that they are alwaysurged into sealing engagement with the adjacent housing surface despitea change in relative position or attitude of the rotor with respect toportions of the housing. When the many individual parts of the rotarymechanism have been manufactured it is necessary to assemble the sealsand their associated springs in grooves in the rotor and position therotor in the housing of the engine. In the case of a rotary enginehaving a three lobed rotor, three apex seals, six corner seals and 12side seals may be carried by each rotor. Most, if not all, of theseseals are spring-biased. Heretofore mechanical clamps or bands, or eventape have been employed to retain the spring-biased seals in theirgrooves when the rotor is being transported to an assembly area and/orwhen the rotor is being positioned in a housing. After the rotor hasbeen positioned in the housing it is necessary to remove the holdingdevices so that the engine may function properly.

It is an object of the present invention to provide a method ofassembling a rotor and its associated springbiased seals in the housingof a rotary mechanism wherein a waxy, adherent, lubricant composition isemployed to temporarily retain the seals in the rotor grooves and, ifdesired, in a recessed position against a spring force during engineassembly.

It is a more specific object of my invention to provide a method ofassembling the rotor and associated springbiased seals in the housing ofa rotary mechanism wherein a petroleum wax based composition is appliedto some or all of the seals before they are inserted in the grooves ofthe rotor. The waxy composition then holds the seals positioned withinthe grooves and in a recessed position, if desired, against the force ofits associated spring during engine assembly. However, after a fewminutes the holding power of the waxy material is overcome and the sealis urged to its normal operating position by the spring so that theengine can be started. Upon engine operation the waxy composition isconsumed leaving no residue.

In accordance with the preferred embodiment of my invention, these andother objects and advantages are accomplished by providing individualmanufactured components of the rotary engine, including the varioussections of the housing, the crankshaft, the rotor, and the seals andsprings in a clean condition. A thin film of a petroleum wax basedcomposition, 2 or 3 mils in thickness, is applied to the side surfacesof the apex seals, the side seals, and if desired to the cylindricalsurfaces of the corner seals. These seals and their associated springsare then placed in the intended grooves of the rotor. During theassembly of the seals in the rotor,

the film on the sides of the seals rubs against the adjacent walls ofthe grooves, adhereing thereto and holding the respective seals inplace. Typically the apex seals will be pushed down into a recessedposition in their grooves against the spring force of their associatedsprings. The rotor is then placed in the housing of the mechanism andthe engine is fully assembled. Over a period of minutes a seal urged byits spring will assume its normal operating position, and thereafterwhen desired the engine may be started. As the engine warms up, the waxcomposition employed in the assembly of the seals will first act as alubricant for the sliding seals but will ultimately evaporate and beconsumed and removed with exhaust products of the engine. No residue isleft in the engine to corrode its parts or impede its operation. Thereis no need to remove any mechanical device which might otherwise havebeen employed in connection with the assembly of the seals and the rotorin the engine housing.

A better understandind of my invention will be obtained from a detaileddescription thereof which follows. In connection with the description,reference will be made to the drawings in which:

FIG. 1 is a sectional view of a partially assembled rotary engine;

FIG. 2 is a perspective view of a rotor and its associated seals; and

FIG. 3 is a schematic drawing depicting one means of applyingthe.adherent lubricant composition to the side surfaces of an apex seal.

The waxy, adherent, lubricant composition employed in accordance with myrotary engine assembly process preferably incorporates amicrocrystalline petroleum wax. Petroleum wax contributes adherency andbody to the composition used during the assembly of the springbiasedseals. After the engine has been started the waxy composition brieflyserves as a lubricant until it is vaporized and burned from the enginewithout residue. Other suitable vaporizable and combustiblehydrocarbon-like materials may be mixed with the wax to modify itsproperties in this application. For example, liquid polybutenes having anumber average molecular weight of about 2,500 to 3,000 can be mixedwith a microcrystalline petroleum wax to increase its tack and desirablerelease properties. A composition consisting of about 70. percent byweight of a microcrystalline petroleum wax having a specific gravity ofabout 0.85 and a melting range of about to F. and about 30 percent byweight of a liquid polybutene is particularly useful in the practice ofmy process. The mixture is prepared by melting a measured quantity ofthe wax and stirring in the polybutene and then cooling.

Other waxy compositions are suitable for use in the practice of myprocess. A mixture consisting, by weight, of 40 percent liquidpolybutene, 30 percent amorphous polypropylene of relatively highmolecular weight, 20 percent microcrystalline petroleum wax and 10percent hydrogenated wood rosin has been used. This composition islikewise prepared by heating and mixing the components together.

The above-described tacky lubricant formulations are to be deemed onlyas illustrative of the waxy compositions which may be employed in thepractice of my process. A thin film of such a material of the order oftwo to three mils thickness is applied by any suitable method tosurfaces of apex seals, side seals and/or corner seals of the rotarymechanism which will lie adjacent to the walls of a groove in the rotorwhen the seal is inserted therein. The grooves are normally machined toprovide a small clearance for the seal, and the lubricant film issmeared upon and adheres to the side wall of the groove when the sealand its spring is inserted therein. The tacky lubricant temporarilyholds the seal in place even in a recessed position against the force(upwards of 7 /2 lbs or so) of its spring tending to urge the seal outof the groove.

The assembly of a rotary engine employing my method will now be morefully described. Typically, a first end housing, indicated at 10 in FIG.1, is placed on a bench or in a suitable fixture. The rotor housing 12is placed on top of the end housing 10. The crankshaft 14 is insertedinto the end housing 10. A rotor 16, with its apex seals 18 and apexseal springs 20, side seals 22 and side seal springs 24, and cornerseals 26 all previously assembled in the proper grooves, and theeccentric 28 are threaded over the crankshaft 14 and positioned in theproper location or orientation for proper engine timing.

In accordance with my invention the side seals and comer seals maysimply be held in place by the lubricant composition so that they do notfall out as the rotor is handled, shipped and placed in the rotorhousing. The lubricant film 30 applied to the surfaces of the side seal22 and the corner seal, as indicated in FIG. 2, is very effective inholding the seals in place. However, it is usually preferred to depressat least the apex seals 18 for insertion of the rotor in the rotorhousing. Referring to FIG. 2, it is seen that my lubricant compositionis suitably applied to both side surfaces of an apex seal as indicatedat 32. Each seal and its spring are then pushed into the groove in arecessed position as indicated at 34 of FIG. 2. The lubricant film holdsthe apex seal in a recessed position until the rotor can be placed inthe rotor housing. In the case of a typical two-rotor mechanism, theintermediate housing is then placed over the first rotor and the secondrotor housing is placed over the intermediate housing. The proceduredescribed above with respect to the first rotor and its associated sealsis repeated with respect to the second rotor. The last end housing isthen placed over the second rotor and the engine is bolted together, andthe assembly completed by attaching the spark plugs, distributor,carburetor and the like. By the time the engine is ready to be given itstrial run those seals which were initially in a recessed position willhave been slowly urged out to their operating position, as illustratedfor example with respect to an apex seal 18 at 36 in FIG. 2. With theseals in their proper positions the engine can be started. As the engineis started and reaches operating temperature the waxy composition firstdecreases in viscosity to better serve as a lubricant for the seals. Thecomposition is eventually evaporated and burned out of the engineleaving no residue which might corrode the engine or otherwise adverselyaffect its operation.

The composition employed in accordance with this assembly process may beapplied to appropriate surfaces of rotor seals in accordance with any ofa number of suitable techniques. The composition can initially be castfrom a hot melt in the form of a crayon and rubbed onto one or moresides of a seal to form a film coating thereon. In another procedure afilm of the composition can be applied by a hot melt gun which heats andextrudes the composition onto the side of a seal. A method which hasbeen found to be particularly suitable is to initially apply a thinlayer of the composition, about 2 to 3 mils in thickness, to a strip ofrelease paper. Preferably the release paper is about 7/16 inch wide andof indefinite length. A layer 38 of lubricant composition 3/16 inch inwidth can be applied to the paper 40 and then readily transferred bypressure, such as by a roll 42 as depicted in FIG. 3, at ambienttemperature to an apex seal 18 or other seal. The strip of layerlubricant formulation 38 releases from the sized release paper 40 and istransferred by pressure to form a film 32 on the apex seal 18.

Normally it is preferable to coat apex seals on both sides so that theycan be suitably held in a recessed position. Side seals may suitably becoated on only one side since it may not be necessary to hold them in arecessed position but only to maintain them in the rotor groove. Thecomer seals are keyed with the apex seals and the adherent lubricant onthe apex seal is frequently sufficient to hold the comer seal.

The described adherent, lubricant compositon may be employed inaccordance with the subject assembly method although the composition ofthe seals and rotor may vary from application to application. Typicallythe rotor is formed of a ferrous base material such as steel or castiron and may also be formed of aluminum in accordance with my assemblymethod. The seals may be formed of any suitable metal, carbon-metalcomposite or other suitable material and still be compatible with thepractice of my assembly method.

While my invention has been described in terms of a preferred embodimentthereof, it will be appreciated that other forms may readily be adoptedby one skilled in the art. Accordingly, the scope of my invention is tobe considered limited only by the following claims.

What is claimed is:

1. A method of assembling components of a rotary engine of the typehaving an outer housing body including a cavity, a rotor disposed insaid cavity for relative rotation with said outer body, said rotorhaving a plurality of grooves with at least one groove containing aspring-biased seal member such that in the operation of said mechanismsaid seal member is urged into sealing engagement with a surface of saidhousing body, said method comprising providing a said rotor, and a saidseal member and spring in substantially finished manufactured conditionready for assembly, applying a film of adherent lubricant composition toa surface of said seal which lies adjacent a wall of a said rotor groovein the operation of said engine,

inserting said spring and seal in said groove and pushing said sealagainst said spring so that said seal is depressed in said groove belowthe normal operating position of said seal, said composition adhering tosaid groove wall and holding said seal in said depressed position whilesaid rotor is placed in said housing,

and then placing said rotor including said springbiased seal in saidhousing, said seal subsequently being returned to its operating positionby said spring, said composition being removable from said engine byvaporization and combustion during the operation of said engine.

2. A method of assembling components of a rotary engine of the typehaving an outer housing body including a cavity for a rotor, a rotordisposed in said cavity for relative rotation with said outer body, saidrotor having a plurality of grooves each adapted to receive a spring anda seal member such that in the operation of said engine a said-sealmember moves in a said groove and is urged by a said spring into sealingengagement with a surface of said housing body, said method comprisingproviding a said rotor and said seal members and springs insubstantially finished manufactured condition for assembly,

applying a film of adherent waxy composition to a surface of each saidseals which surface will in the operation of said engine slide against awall of a said rotor groove,

placing each of said springs and its associated seal in appropriategrooves of said rotor,

pushing in at least one of said seals against its spring so that saidseal is depressed in its groove below the normal operating position ofsaid seal, said waxy composition adhering to said groove wall totemporarily hold said seal in said depressed position while said rotoris placed in said housing,

and then assembling said rotor in said housing, said seal being returnedto its operating position after said assembly by the force of saidspring overcoming the adherence of said composition, said compositionbeing removable from said engine by vaporization and combustion duringthe operation of said engine.

3. A method of assembling components of a rotary engine of the typehaving an outer housing body including a rotor cavity, a rotor disposedin said cavity for relative rotation with said outer body, said rotorhaving a plurality of grooves each adapted to receive a springbiasedapex seal member such that in the operation of said engine each of saidapex seal members is urged into sealing engagement with a surface ofsaid housing body, said method comprising providing a said rotor andsaid apex seal members and associated springs in substantially finishedmanufactured condition ready for assembly, applying a film of anadherent waxy composition to the side surfaces of said apex seals,inserting each of said apex seals and associated springs in a groove ofsaid rotor, pushing each of said apex seals against its associatedspring so that said apex seals are depressed in their grooves belowtheir normal operating position, said composition adhering to thesurfaces of said seals and said grooves so as to temporarily hold saidseals in said depressed position while said rotor is placed in saidhousing, and then assembling said rotor and its spring-biased apex sealsin said housing, each of said apex seals being returned to their normaloperating position after said rotor has been assembled in said housingby the force of its spring overcoming the adherence of said composition,said compositon then being removable from said engine by vaporizationand combustion during the operation of said engine.

1. A method of assembling components of a rotary engine of the typehaving an outer housing body including a cavity, a rotor disposed insaid cavity for relative rotation with said outer body, said rotorhaving a plurality of grooves with at least one groove containing aspring-biased seal member such that in the operation of said mechanismsaid seal member is urged into sealing engagement with a surface of saidhousing body, said method comprising providing a said rotor, and a saidseal member and spring in substantially finished manufactured conditionready for assembly, applying a film of adherent lubricant composition toa surface of said seal which lies adjacent a wall of a said rotor groovein the operation of said engine, inserting said spring and seal in saidgroove and pushing said seal against said spring so that said seal isdepressed in said groove below the normal operating position of saidseal, said composition adhering to said groove wall and holding saidseal in said depressed position while said rotor is placed in saidhousing, and then placing said rotor including said spring-biased sealin said housing, said seal subsequently being returned to its operatingposition by said spring, said composition being removable from saidengine by vaporization and combustion during the operation of saidengine.
 2. A method of assembling components of a rotary engine of thetype having an outer housing body including a cavity for a rotor, arotor disposed in said cavity for relative rotation with said outerbody, said rotor having a plurality of grooves each adapted to receive aspring and a seal member such that in the operation of said engine asaid seal member moves in a said groove and is urged by a said springinto sealing engagement with a surface of said housing body, said methodcomprising providing a said rotor and said seal members and springs insubstantially finished manufactured condition for assembly, applying afilm of adherent waxy composition to a surface of each said seals whichsurface will in the operation of said engine slide against a wall of asaid rotor groove, placing each of said springs and its associated sealin appropriate grooves of said rotor, pushing in at least one of saidseals agaiNst its spring so that said seal is depressed in its groovebelow the normal operating position of said seal, said waxy compositionadhering to said groove wall to temporarily hold said seal in saiddepressed position while said rotor is placed in said housing, and thenassembling said rotor in said housing, said seal being returned to itsoperating position after said assembly by the force of said springovercoming the adherence of said composition, said composition beingremovable from said engine by vaporization and combustion during theoperation of said engine.
 3. A method of assembling components of arotary engine of the type having an outer housing body including a rotorcavity, a rotor disposed in said cavity for relative rotation with saidouter body, said rotor having a plurality of grooves each adapted toreceive a spring-biased apex seal member such that in the operation ofsaid engine each of said apex seal members is urged into sealingengagement with a surface of said housing body, said method comprisingproviding a said rotor and said apex seal members and associated springsin substantially finished manufactured condition ready for assembly,applying a film of an adherent waxy composition to the side surfaces ofsaid apex seals, inserting each of said apex seals and associatedsprings in a groove of said rotor, pushing each of said apex sealsagainst its associated spring so that said apex seals are depressed intheir grooves below their normal operating position, said compositionadhering to the surfaces of said seals and said grooves so as totemporarily hold said seals in said depressed position while said rotoris placed in said housing, and then assembling said rotor and itsspring-biased apex seals in said housing, each of said apex seals beingreturned to their normal operating position after said rotor has beenassembled in said housing by the force of its spring overcoming theadherence of said composition, said compositon then being removable fromsaid engine by vaporization and combustion during the operation of saidengine.